This invention relates to a process for the manufacture of high solids, granular poly(dimethyldiallyl ammonium chloride) [hereinafter referred to as "poly(DMDAAC)"], which is free-flowing and highly soluble. Additionally, the poly(DMDAAC) prepared by this process has a high molecular weight and better performance characteristics than poly(DMDAAC) prepared by conventional solution polymerization techniques.
More particularly, the invention described herein is a continuous polymerization process for the preparation of improved poly(DMDAAC) which utilizes a combined visible light and thermal initiation system.
Many processes are known in the art for the preparation of water-soluble polymers. For example, water-soluble polymers have been prepared in solution, in suspension and in emulsion using chemical initiators. These processes, however, generally result in low conversion, low concentration of product and varying product quality. Additionally, various other polymerization processes have been proposed, as for example, photopolymerization processes such as those disclosed in U.S. Pat. Nos. 2,850,445; 2,880,152; 2,880,153; 4,306,955; 4,308,148; 4,325,794; 4,415,417; 4,252,625; 4,178,221; and 3,912,607 and high energy or radiation processes such as the one disclosed in U.S. Pat. No. 3,926,756.
The above referenced processes suffer from a variety of disadvantages, including high capital and manufacturing costs, low conversion, high energy requirements and low initial monomer concentration. Additionally, product forms such as emulsions, powders, dilute solutions and suspensions have inherent problems. For example, emulsification may deleteriously affect polymer performance, while oil and surfactant requirements keep manufacturing costs high. Powdered polymers are costly to produce due to the drying and milling steps required, and these operational steps may also degrade polymer quality. Dilute solutions of water-soluble polymers may be easy to handle, but are costly to transport due to their low active polymer content.
Accordingly, the need exists for a low cost method of preparing poly(DMDAAC) which can be easily and economically handled, and which has improved performance characteristics, high molecular weight, and high polymer concentration. Such an invention would satisfy a long felt need and constitute a notable advance in the art.
It is therefore an object of this invention to provide a process for the preparation of a high solids, granular form of poly(DMDAAC).
It is a further object of this invention to provide a process for the preparation of high solids, granular poly(DMDAAC) which reduces capital and operating costs.
It is a further object of this invention to provide a high solids, granular poly(DMDAAC) which is easy to handle, free-flowing, and highly soluble.
It is a still further object of this invention to provide a high solids, granular form of poly(DMDAAC) which has a higher molecular weight and better performance characteristics than poly(DMDAAC) prepared by conventional solution polymerization techniques.
These and other objects of this invention are accomplished by a process in which visible light is used to activate polymerization of a thin film, high solids dimethyldiallyl ammonium chloride (DMDAAC) monomer solution. This monomer solution may optionally contain not greater than 5 percent, by weight, of at least one additional water-soluble, ethlenically unsaturated monomer which is polymerizable with DMDAAC monomer. After polymerization commences, a thermal initiator is used to enhance the polymerization. When the exotherm raises the temperature of the polymerization system to a level sufficient to activate the thermal initiator, the light source may optionally be shut off. The reaction is then continued by the heat released from the polymerization process. This reduces the energy requirements of this process and permits higher conversion of monomer to polymer. Additionally, this allows the use of a smaller bank of lights when the manufacturing process is continuous.
A second aspect of this invention relates to a novel product form for poly(DMDAAC). The unique products made by the inventors' process are free-flowing, high molecular weight, high solids granules of poly(DMDAAC). These granules remain free-flowing and readily soluble after storage for extended periods of time.